Phototube housing with selectable filters



oct. 11, 1949.` M. H. SWEET 2,484,323

PHOTO TUBE HOUSING WITH SELECTABLE FILTERS* v Filed Sept. 17, 1948 Fig.

INVENTOR Monroe H. Sweet ATTORNEY BY1 1... Cw 4544; #MSW Patented Oct. 11, 1949 PHOTOTUBE HOUSING FILTERS WITH SELECTABLE I Monroe Hamilton Sweet, Binghamton, N. Y., as-

signor to General Aniline & Film Corporation,`v New York, N. Y., a corporation of'Dclaware- Application september 17, 194s, serial 10.49354 6 Claims.` (C1. Z50-239) This invention relates to photographic apparatus and more particularly to a housing for phototubes accommodating a series of selectable filters.

In photo-electric devices it is often necessary to employ various types of lters between the light source and the tube. In certain `applications, for example, in densitometers which measure the relative density of color positives, filters of different colors are used which must be placed between the photocell and the specimen in order to determine the absorption characteristics of the material at various wave lengths.

Filters of this type have heretofore been used manually or placed on a at disc which revolved thus permitting selected insertion of the filters. This type of construction has the disadvantage that when high densities are encountered, stray light entering the device is apt to cause a large error in the indication.

Particularly in photo-electric tube circuits which employ a multiplier type phototube resulting in a high degree of amplification, it is extremely important to have the tube completely shielded from light as well as electrostatic effects. The housing of such phototubes must have a light tight construction and must offer also good electrical shielding.

A particular feature of this invention is the novel construction of housing for phototubes which excludes light completely and at the same time incorporates means for selectively inserting a series of filters without the danger of stray light entering the phototube.

A particular advantage of the structure in accordance with this invention is the compactness ofv assembly which includes the lter holder within the phototube housing and permits the selection with ease of the particular filter desired from outside of the housing.

Another advantage of the invention resides in the means for excluding stray light completely between the filter and the phototube as well as between the housing and the lter.

Other features and advantages will be apparent from the following description of the invention, pointed out in particularity in the appendent claims and taken in connection with the accompanying drawing in which:

Fig. 1 is a sectional view of the housing, showing the lter holder therein, and;

Fig. 2 is a cross sectional view of the complete housing along the lines 2-2 of Fig. 1.

Referring to the gures, the phototube housing comprises a U-shaped casing 3 which may be of cast aluminum or other suitable metal. The bot- 2 tom part of the casing is recessed to accommodate a flat bottom plate II.l Inthe gures only the part of the phototube housingis shown which incorporates the improvements to which this invention is directed.` The rest of the structure may have any desired shape, depending upon the particular use to which the photocell is employed. For example, in a densitometer device the housing may terminate in alhinged portion pvoted in a suitable holder whereby it may be lifted up in order to place aspecimen on the table on which the plate 4 of the housing may .normally rest. This type oi housing construction is described and illustrated in Electronics Magazine (November 194,6, pag,es' 10x5-1(I)9)` in connection with a densitometer instrumentl designed by the originator of this invention. Y

Thebottom plate I has an aperture accommodating a grommet 5, which is ,of resilient material such as rubber, and extends into the space between the inner wallof the bottom plate Il and the rotatable sleeve 6;, the purpose of which will be apparent upon further consideraton of the structure. The sleeve t is of a cylindrical shape and hollow. At one end it is closed and a shaft extends therefrom through the front portion of the casing 3 in which it revolves ina bearing 8. The end of the shaft 1 carries a knob 9 for rotation by hand of theI sleeve 6. This knob may have a knurled surface' and engagea pin I Il so as to prevent accidental rotation of the sleeve 6 after a selected position. y

The cylindrical side of the sleevev 6 has a series of circumferentially distributed apertures each of which forms a holder for a lter I2 which coopcrates with the aperture formed by the grommet 5. It is to be noted that the latter extends in close proximity to the lter holdingportion of the sleeve B. The reason for this is to form a lighttight 'coupling between the sleeve and the aperturein the wall of thehousing formed by the bottom plate il. In this manner stray light is excluded which otherwise lcould easily enter the aperture and, as mentioned before, would adversely affect the accuracy of the instrument when high densities are encountered.

Inside the casing 3 and affixed thereto in a flexible band I3 the circumferential length of which is adjustable by means of the screw I4. The purpose of this band is to hold a phototube I5 in position within the housing and it is so dimensioned as to iit over the base I6. In this manner the tube I5 can easily be positioned to have its photoactive element in proper alignment with the aperture in the plate 4. When the band I3 is loose the tube I can be rotated as Well as moved axially until proper alignment is obtained. With the screw tightened the band I3 will securely hold the base i5. A socket for the phototube may also be accommodated in the rest of the housing, not shown, together with other circuit components which require carefulshieldingddepen-ding on the over-allsize of thehousing cliosento satisfy a particular type of apparatus.

From the above description it is clearly seen,

that in any position of the housing oneof a series of iilters may instantly be inteifps'edby simply turning the knob 9. with the sample through whichdig-ht intensityv 1smade to energize the photctubesand-strayjlight cannot enter the active eltendent-ofithe"-tubel` no matter what position they housing may be or what particular lter is bei'ngused' Th'eirotat'- ing sleeve 6, aside from carrying the-:filters: lf2 provides additional shielding and protection for the phototube-I5 and adds. to the necessary increased weight which "'is"'d''s"ir'able at this' endl' of thev housing: inasiriuenj as' it u'si'iali'yA restso'ri` a sample! the' surface oi" 'wl "his 't'ozbeexplore'd.

Whil'efonly'one ein d nt of' the invention riasbeen disciosedji it si to'v be understood that the inventive f concept" may carried' 'out' a" 'num'- ber Of Ways; ti0h"iS,` therefore," not to be limited to the' preeise'detaiis described but is intended to coi/felix" all" variaticjn's" and `mo'di'` cations" therbf falling"-w`ithnf`tlie Spirit' Of` the invention' and the" scope or the"cla'ims;`

1.` In com'binatib'ni' a" pnotolelectric tube; a' housing forsaid`tu epvidingco'nplete shield'- ing. from'putside liglt an'vv'alll fsaidhqusin'g denning an apettore,"` the pnotoactive" element of said tube being aligned-with" saidA aperture, means for. inserting" a. filter between-said" tube and said: a'pertujre-V comprising sleeve rota'tame over the tube havin'g ai.' p1uralitt'f,"ofA receptacles each accommodating-a' nltef, and' njieaiis outside of said housing'for?rotating,saidsleeve'whereby aj desired citer be: interposed. between the tubeand'vtl'el a'perturer said"`lio'l`1singl' 2..In` c 'o'mbiii'a'.'tfi'on'` a plotleletric. tube',t a housing* for"'saidftpe' providing complete ysiiitniing. from odtsid'eiight, a wallk for saidj housing denningari aperture; the"pnotaotiveeiement of said tube being" alignedwitlsaid a'p" ure,-A means for inserting: a desired1 clrfii'iter between Lsaid-j tube'and sai'd aperture' compri "'a cylindrical sleeve rotatable over the 'tu gN apluralit'y' orV circumferentiaiiyarrange reeeptacles'in' the wall of said sleeve each" aridoI'nir''oclatingl ain-ter and means outside' of said' li''iisi'ig"y for rotating said' sleeve whereby' a desired alter be'. in'- terposed between the" tube andtlieapertur in said'housing.' y

housing l definingJ an' abertine;` tiiephotoaotive This in no way interfereselement of said tube being aligned with said aperture, means for inserting a desired color lter between said tube and said aperture comprising a cylindrical sleeve rotatable over the tube having a plurality of circumferentially disposed iilters in the Wall of said sleeve, means outside of saidhousing-ion rotating said sleeve comprising a shaft extending from said portion and `J'ournaled therein and a knob on said shaft whereby a desired lter may be interposed between said tube and said aperture.

v 411. In combination a photo-electric tube, a housing for said tube providing complete shielding. from outside light, a wall for said housing .'Jdeii'n'ing' an! aperture, the photoactive element oil'saidf-tubefbeingil aligned With said aperture, means for inserting a nlter between said tube Y andfsaid#apertiire'lcomprising a sleeve rotatable oven thetube having a plurality of receptacles each accommodating aiilter and means outside of said housing for rotating said sleeve and means for excluding straylightv from entering thejspace4 `between 'said aperture" and said sleeve. 5"? In combination' a' photo-electric'. tube,h a housing for said tube providing complete shieldingfrom' outside light, avwall" frsaidhousingdefining an aperture'. the plfoto'a'ctiv'e element of' said'tube being' aligned.'y with said! aperture, means for insertinga" nlterbetween saidltube and said' aperture comprising al sleeve rotatable over'V the tubehaving' at plurality' of receptacles each accommodating a" iilter ande meansw outside of said housing flor'r'ota'tin'g sa'idlslefeveandimeans for excludingfstray;light'from entering'tbe space between said'aperture' and'fsaid' sleeve comprisingv aresilient' grommet' surrounding. the ap'er# ture'dening edges' of said wall and extending t'o' the'outer peripheral surface ofsa'id' sleeve' 6; In` combination, a," photo-electric. tube' of elongated. construction, a housin'g'ior'said tube comprising a'Y Ufsli'aped'cover portionand" a' fiat portion having an aperture extending between the' legs ofvv said" VU'eshaped',c'o'ver, and'` a' front walllaccomm'odating ai shaft' extending. there'- tlirough aXiaIIy'O'Saidtube, a cylindrical'sleeve affixed to said shaft inside' said' housing and' a knob afiix'ed" to said 'shati outside said, housing whereby said sleeve Hmay be rotated, the wall oi"- saidf cylindrical sleeve d'ening a" series' of concentrically arranged' apertures each' accommo'datin'g a filter, an adjustable lleXible b'a'nd f'o'rfholding said tube securedto the" inner wall'of said" housing and circumferentially envelor'iimg;`

the base of said tube permitting longitudinal/as' No references cited.'A 

